Question: Non-centered copped X-Ray

[poretga99]

I want to perform DRR rendering with reference geometry given in transformation matrices instead of the C-arm parameters and can't get the same result as our internal rendering engine.

Given the following matrices given in DICOM coordinate system:

TPos: 4x4 homogenous matrix, representing the detector position in WCS SPos: 3x1 vector, representing X-Ray source position in WCS

How can one properly construct the geometry? I can expose the SSD by calculating the distance from source location (SPos) to X-Ray detector plane, but the ray does not need to directly intersect with the detector midpoint.